Well, it's written in Chinese pinyin. If you're a beginner, it's a bit confusing. ta(1 ) could refer to both male and female when it's written in pinyin. Although, if it was in the character form 他or 她 it wouldn't be so ambiguous. Tā xiǎo de shíhou bù rènshi tā. The meaning of this sentence can be either way as follow " when he/she was young, didn't know him/ her". I hope this helps a little. Good luck.